Retroreflective materials have been developed for use in a variety of applications, including road signs, license plates, footwear, and clothing patches to name a few. Retroreflective materials are often used as high visibility trim materials in clothing to increase the visibility of the wearer. For example, retroreflective materials are often added to protective garments worn by firefighters, rescue personnel, EMS technicians, and the like.
There are two major types of retroreflective materials: beaded materials and cube-corner materials. Beaded materials typically use a layer of tiny glass beads or microspheres that cooperate with a reflective agent, such as a coated layer of aluminum. Cube-corner materials typically employ a multitude of cube-corner elements to retroreflect incident light.
Retroreflective materials can be particularly useful to increase the visibility of fire and rescue personnel during nighttime and twilight hours. In some situations, however, firefighter garments can be exposed to elevated or extreme temperatures over an extended period of time, causing the retroreflective material to trap heat inside the garment. Under certain conditions, the trapped heat can result in discomfort to the skin of the firefighter.
It's desirable to have vapor-permeable retroreflective trim. Attempts have been made to achieve this, e.g., by forming needle-punched openings through all the layers comprising a retroreflective article that is attached to a garment. However, this solution could potentially exacerbate the problem of trapping water and other materials (which can hold heat) beneath the trim. When the retroreflective article is attached to the garment, e.g., by sewing, a cavity is formed under the retroreflective article. If the openings extending through the retroreflective article are large enough, they can allow vapors, liquids, and suspended solids, including water and chemicals, to enter and collect in the cavity. While water and other vapor-forming materials might eventually pass back through the openings, it is likely that any solids will be left behind in the cavity, and would be virtually impossible to remove.